The invention relates to a method for testing digital circuitry. In general, digital full swing high speed data transmission between two integrated circuit chips necessitates the use of a wide-frequency spectrum. Therefore, actual data transmission is very frequency sensitive. To reduce frequency sensitivity, it is better to send an analog low swing bit stream instead of digital data. Now, for sending analog bit streams, an analog low swing interface (LSI) is necessary; note that this abbreviation has a different meaning from everyday usage in electronic technology. To ensure correct functionality of this interface it is these low swing interface signals should be rendered digitally testable. However, a standard manufacturing test machine cannot handle the analog input and analog output signals. Therefore, a specific test interface facility should be provided, for executing the actual digital manufacturing tests.